New minerals tsangpoite Ca5(PO4)2(SiO4) and matyhite Ca9(Ca0.5□0.5)Fe(PO4)7 from the D'Orbigny angrite

Tsangpoite, ideally Ca5(PO4)2(SiO4), the hexagonal polymorph of silicocarnotite, and matyhite, ideally Ca9(Ca0.5□0.5)Fe(PO4)7, the Fe-analogue of Ca-merrillite, were identified from the D'Orbigny angrite meteorite by electron probe microanalysis, electron microscopy and micro-Raman spectroscopy. On the basis of electron diffraction, the symmetry of tsangpoite was shown to be hexagonal, P63/m or P63, with a = 9.489(4) Å, c = 6.991(6) Å, V = 545.1(6) Å3 and Z = 2 for 12 oxygen atoms per formula unit, and that of matyhite was shown to be trigonal, R3c, with a = 10.456 (7) Å, c = 37.408(34) Å, V = 3541.6 (4.8) Å3 and Z = 6 for 28 oxygen atoms per formula unit. On the basis of their constant association with the grain-boundary assemblage: Fe sulfide + ulvöspinel + Al-Ti-bearing hedenbergite + fayalite-kirschsteinite intergrowth, the formation of tsangpoite and matyhite, along with kuratite (the Fe-analogue of rhönite), can be readily rationalised as crystallisation from residue magmas at the final stage of the D'Orbigny meteorite formation. Alternatively, the close petrographic relations between tsangpoite/matyhite and the resorbed Fe sulfide rimmed by fayalite + kirschsteinite symplectite, such as the nucleation of tsangpoite in association with magnetite ± other phases within Fe sulfide and the common outward growth of needle-like tsangpoite or plate-like matyhite from the fayalite-kirschsteinite symplectic rim of Fe sulfide into hedenbergite, infer that these new minerals and the grain-boundary assemblage might represent metasomatic products resulting from reactions between an intruding metasomatic agent and the porous olivine-plagioclase plate + fayalite-kirschsteinite overgrowth + augite + Fe sulfide aggregates. Still further thermochemical and kinetics evidence is required to clarify the exact formation mechanisms/conditions of the euhedral tsangpoite, matyhite and kuratite at the grain boundary of the D'Orbigny angrite.Fil: Hwang, Shyh Lung. National Dong Hwa University; República de ChinaFil: Shen, Pouyan. National Sun Yat-sen Universit; República de ChinaFil: Chu, Hao-Tsu. Central Geological Survey; República de ChinaFil: Yui, Tzen-Fu. Institute of Earth Sciences; República de ChinaFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Iizuka, Yoshiyuki. Institute of Earth Sciences; República de Chin

The Tectono-Thermal Events of Taiwan and Their Relationship with SE China

We present a new synthesis of the tectono-thermal events of Taiwan, excluding the Coastal Range, based on existing isotopic, geochemical and geochronological data for granitic, metamorphic, volcanic and sedimentary rocks. Nd model ages (TDM) and the inherited zircon ages consistently yielded Proterozoic ages, suggesting that the source rocks from the exposed rocks in Taiwan were formed in the Proterozoic, starting from about 2 Ga ago. The crustal evolution of Taiwan began in the Late Paleozoic (250 ¡_ 20 Ma). Since then, five tectono-thermal events can be delineated: (I) an Early Jurassic event (200 - 175 Ma) registered in the marble and metapelites of the Tananao metamorphic basement complex of northern Taiwan and crystalline limestone of the basement rocks in western Taiwan; (II) a Late Jurassic event (~153 Ma) revealed by a meta-granite of the Tananao metamorphic basement complex of southern Taiwan; (III) a Late Mesozoic event (97 - 77 Ma) recorded in the rocks of the Tananao metamorphic basement complex and offshore of northern and western Taiwan; (IV) a Cenozoic of pre-Pliocene event (episodic from 56 to 9 Ma) registered in the dikes in the Central Range and the intraplate basalts of mainland Taiwan and offshore of northern and western Taiwan; and (V) an ongoing Late Cenozoic event (since 5 Ma) shown in the recent volcanics of onshore and offshore northern Taiwan and offshore northeastern Taiwan

High pressure/ultrahigh pressure eclogites from the Hong'an Block, East-Central China : Geochemical characterization, isotope disequilibrium and geochronological controversy

The Hongan Block (western Dabieshan) exposes a series of HP/UHP metamorphic rocks, with a S-to-N distribution from blueschist­greenschist, kyanite-free, to kyanite- and coesite-bearing eclogites. The available age data are inconclusive that hinder our understanding of the tectonic evolution of the Block. The metamorphic temperatures in the Hongan Block (Tmeta 700 to 500°C) are lower by 50­150°C than that of the Dabie and Sulu terranes. In this work, we undertook new trace element and Sr­Nd­O isotopic analyses on minerals in order to gain more insight into the geochronological problems. The results are as follows: (1) Trace element distribution patterns suggest that garnet and omphacite in many cases are out of chemical equilibrium; and the presence of high-temperature LREE-rich mineral inclusions (e.g., epidote) in garnet and omphacite has contributed to isotope disequilibrium. (2) Sm­Nd isotope analyses yielded no isochron ages for the Hongan eclogites. (3) Rb­Sr isotope analyses gave mixed results; in some cases, coexisting minerals are completely out of isotope equilibrium, and in others, isochron relationship is established, yielding ages from 210 Ma to 225 Ma. The pattern of Rb­Sr isotope disequilibrium appears to be independent of the petrological and O-isotope temperatures. (4) In contrast to the unequilibrated Sm­Nd isotopic systems, oxygen isotopes of the eclogite minerals seem to have attained isotope equilibrium or near-equilibrium. Oxygen isotope temperatures are comparable with petrological temperatures. However, this is an apparent feature due to mass balance constraints. (5) Whole-rock 18O values show a large variation from +10 to ­8, suggesting that their protoliths have undergone very different processes of water­rock interaction. In view of the overall geochronological information, we conclude that the HP/UHP metamorphism in the Hongan Block took place in the Triassic at about 220­230 Ma, as observed in the Dabie and Sulu terranes. The significance of published Paleozoic dates (450­300 Ma) for the Xiongdian eclogite is not clear. However, any hypotheses advocating two periods of UHP metamorphic events for the same tectonic unit or in the same locality are not constrained by the geochronological data

Kuratite IMA 2013-109

The information given here is provided by the IMA Commission on New Minerals, Nomenclature and Classification for comparative purposes and as a service to mineralogists working on new species.Fil: Hwang, Shyh-Lung. National Dong Hwa University. Department of Materials Science and Engineering; República de ChinaFil: Shen, Pouyan. National Sun Yat-sen University. Institute of Materials Science and Engineering; República de ChinaFil: Chu, Hao-Tsu. Central Geological Survey; República de ChinaFil: Yui, Tzen-Fu. Academia Sinica. Institute of Earth Sciences; República de ChinaFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; ArgentinaFil: Iizuka, Yoshiyuki. Central Geological Survey; República de Chin